Sen. Rand Paul (R) of Kentucky testifies before a state legislative committee on the legalization of growing hemp at the Capitol Annex in Frankfort, Ky., Monday.

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Washington — On ABC's "This Week," GOP strategist Nicolle Wallace revealed Sunday that Sen. Marco Rubio (R) of Florida – who will deliver the official Republican response to President Obama's State of the Union address – has scrapped his original draft in favor of a more aggressive approach. According to Ms. Wallace, Senator Rubio's decision to rewrite his remarks was spurred by the tone of Mr. Obama's inaugural address, which many Republicans saw as "historically combative."

But we wonder if it's really Obama that Rubio is thinking about – or Kentucky Sen. Rand Paul.

Senator Paul, of course, will be delivering the official "tea party response" to Obama's address, a tradition started two years ago by Minnesota Rep. Michele Bachmann (who famously failed to look into the camera throughout her remarks), and repeated last year by Herman Cain.

Even before they've been delivered, the dual responses are already being cast as yet another example of the base-versus-the-establishment schism in the Republican Party. That division has been on full display in recent weeks, with news of a new, Karl-Rove-backed political group that will aim to weed out "unelectable" far-right candidates in Republican primaries – a move that many tea party conservatives saw as a declaration of war.

Paul told CNN over the weekend that his speech is not intended to be "divisive," but is simply an "extra response." Appearing on "State of the Union with Candy Crowley," he said that while he might emphasize some things that "maybe Marco doesn't" (he cited foreign aid as one example), he wasn't planning to use the occasion to highlight intra-party disagreements: "I won't say anything on there that necessarily is like, 'Marco Rubio is wrong.'"

But there's clearly an emerging rivalry between the two men – both considered likely 2016 presidential candidates – that reflects the larger split within the Republican Party. Paul himself seemed to unintentionally acknowledge this when he added: "I don't always agree [with Rubio], but the thing is, this isn't about he and I [sic], this is about the tea party."

What's particularly interesting in this case is that Rubio – who was recently lauded on the cover of Time Magazine as "The Republican Savior" –has actually been a tea party darling throughout much of his political career. He was one of the most prominent tea-party-backed candidates to win election in 2010, handily beating establishment-favored former GOP Gov. Charlie Crist.

Notably, Amy Kremer, the chair of the Tea Party Express (the group sponsoring Paul's response), went out of her way to praise Rubio in a press release, saying: "We are happy to see that the Republicans have selected Tea Party conservative Senator Marco Rubio to deliver their response. Both Senator Rubio and Senator Paul will articulate pro-growth messages that will resonate with the American people."

But Rubio has also lately taken a high-profile stance on a hot-button issue – immigration reform – that has put him squarely on the opposing side of most tea-party conservatives. And as the unofficial "frontrunner" for his party's nomination, admittedly still years away, he has by definition become more of an establishment figure.

By contrast, Paul is emerging as 2016's most intriguing dark-horse contender. In many ways, he's the inheritor of the independent, outside-the-box mantle of his libertarian father, former GOP Rep. and presidential candidate Ron Paul. But he's also trying to position himself as a more traditionally conservative, tea party candidate in the mold of, say, Representative Bachmann. As someone who clearly isn't taking marching orders from the GOP establishment, Paul could present a real challenge to the eventual party frontrunner – whether Rubio or someone else – and push the entire field to the right.

And that rightward push could begin Tuesday night. The last time Paul and Rubio effectively shared a stage – during the Benghazi hearings, when Hillary Clinton testified – it was Paul who seized the spotlight, with his aggressive questioning of the former secretary of state. He made news by telling her at one point that, had he been president, he would have fired her. By contrast, Rubio's performance came across as mild (less charitable reviewers called it flat), and drew little notice in the press.